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Home , Ferrofluid, Smart fluid

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Indian Journal of Science and Technology Vol. 4 No. 11 (Nov 2011) ISSN: 0974- 6846

Characteristics of ferro

Satish B. Purohit1, S. R. Lapalikar2, Sachin Pare1 and Vikas Jain1

1Mechanical Engineering Department, SGS Institute of Technology and Science, Indore-452002, India 2Principal, Indore Institute of Science and Technology, Indore-452003, India [email protected]

Abstract

This paper focuses on the synthesis and characterization of ferro fluid (). The colloidal mixtures of in carrier fluid were made by different chemical processes. The characteristics like particle size, turbidity, density, , and were studied. The average particle size after repeated filtering measured to 12 nm. The turbidity variation was found to be almost negligible. The damping coefficient varied from 0.2418 Ns/m to 0.8348Ns/m in the . The effect of magnetic field on viscosity was studied on in house made viscometer and calibrated with the existing Redwood viscometer. It was possible to change the viscosity with the change in magnetic field. Such smart fluid could be used in a semi active of a vehicle for better performance.

Keywords: Ferro fluid, viscosity, magnetic field, Smart fluid. Introduction Much research has been centered on ferro that Conventional vehicle suspensions achieve the road contain small particles of magnetite, Fe3O4. Magnetite induced vibration isolation through passive means such can be produced by mixing Fe (II) and Fe (III) salts as springs and dampers or passive shock absorbers. together in a basic solution. The particles must remain With the semi active , the dynamic sag due to small and separated from one another in order to remain body roll in turns can be two to three times smaller. Semi suspended in the medium. Magnetic and van der active suspension system started in the early 1980’s with Waals interactions must be overcome to prevent the the introduction of the first variable damping shock particles from agglomerating into larger particles. Thermal absorbers. These variable dampers typically changed the motion of magnetite particles that are smaller than ~100 damping from soft to firm and vice versa, through a angstroms in size is sufficient to prevent agglomeration manual or slow adaptive control (Hrovat, 1997). The due to magnetic interactions. prevent the variation in damping characteristics of the shock absorber from approaching one another too closely. is done by instantly changing the viscosity of the liquid is a unique material that acts like a magnetic , used as absorber , by changing the magnetic and like a liquid. Each tiny particle is thoroughly field which should be sensitive to road disturbances. coated with a to inhibit clumping. Large Ferro fluid is very much suitable for such applications. ferromagnetic particles can be ripped out of the Ferro fluids (compound of Latin ferrum, meaning , homogeneous colloidal mixture, forming a separate and fluid) are colloidal suspensions of fine (~ 0.05-15 nm) clump of magnetic dust when exposed to strong magnetic dispersions of magnetically soft, multi domain nano fields. The magnetic attraction of nanoparticles is weak particles, such as Fe3O4, coated with surfactants in a enough that the surfactant's van der Waals repulsion is carrier liquid. When there is no magnet nearby, the sufficient to prevent magnetic clumping or agglomeration. magnetite particles in ferro fluid act like normal metal usually do not retain in the particles in suspension. But in the presence of a magnet, absence of an externally applied field and thus are often the particles are temporarily magnetized. Ferro fluids classified as "superparamagnets" rather than respond to an external magnetic field. This enables the ferromagnets. The viscosity of the fluid, the tiny size of fluid’s location to be controlled through the application of the particles, and the particles’ constant motion keep the a magnetic field. The particles are so small in ferro fluids from settling out. that they will not settle over time, but remain in place as Characteristics of ferrofluid and it’s applications have long as a magnetic field is present. Treatment of particles been studied by several researchers. An analytical with surfactants prevents them from clumping up, causing approach based on the coulombian model of a magnet is the material to remain stable and act predictably. They used as a general method for studying the mechanical form structures within the fluid, causing the ferro fluid to properties of a ferrofluid seal. The fundamental Maxwell’s act more like a solid. When the magnetic field is removed, equations define the concept of of the the particles are demagnetized and ferro fluid acts like a ferrofluid seal by using only the three dimensional liquid again. The apparent viscosity of these fluids can be equations of the magnetic field created by ring permanent changed significantly within milliseconds by the radially magnetized (Ravaud & Lemarquand, application of an external magnetic field. 2009). A deformable mirror is made of a magnetic liquid Research article “Smart fluid” S.B.Purohit et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol.

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Indian Journal of Science and Technology Vol. 4 No. 11 (Nov 2011) ISSN: 0974- 6846 whose surface is actuated by a triangular array of small chloride (Fecl₃), steel wool, distilled water, kerosene, current carrying coils and the mirror can correct a 11 μm heater, filter paper. Synthesis Procedure is: reduce FeCl3 low order aberrated wave front to a residual RMS wave to FeCl2, react in 2:1 ratio of FeCl3: FeCl2 in ammonia. front error 0.05 μm. Recent developments show that The Fe3O4will fall out of the solution. Heat the magnetite these deformable mirrors can reach a frequency solution to just below boiling and stir in 5 ml . response of several hundred hertz (Brousseau, 2008). Add kerosene as a carrier fluid. Discard water. The Extensive research work has been done on the fluid second method is to get iron oxide particles of mostly dynamics in the presence of magnetic field for nano spheres, the chemicals used are: Sodiumhydroxide magnetorheological fluids and ferro fluids using the finite (NaOH), Ironchloride (FeCl₃), Sodium element simulation (Tomasz Strek, 2005). It is possible to hexametaphosphate (NaH₂PO₄), Double distilled water. use magnetic fluid to measure volume of non-magnetic Synthesis procedure is: Prepare 0.5 M NaOH solution in body of random shape. Technique is based on the distilled water, Add 0.01 M solution of Fe (NO₃)₃, Stir till detection of change in the of the coil with ferro pH becomes 10.7, Wash the precipitate with distilled fluid as core when body is immersed. Inductance is water several times till pH becomes ~8.7, Add 1 M HCl, related to the volume of the body (Upadhyay Shail, 2006). Stir, Add 0.1 M solution of NaH₂PO₄, Stir, Add water and The motion and shape of a ferro fluid droplet placed in a heat the solution to ~100 deg. Celcius, Wash and dry the non-magnetic viscous fluid and driven by a magnetic field precipitate in air at 100 deg. Celcius. Fe₂O₃ particles are are modeled numerically. The governing equations are obtained. Photographs (Photograph 1) of the ferrofluid the Maxwell equations, equation and prepared by any one of these methods reveal the effect of incompressibility (Afkhami et al., 2008). The drops of a a magnet. The ferrofluid liquid turns into a paste like ferro fluid floating in a non-magnetic liquid of the same material in presence of a magnet. density and spun by a rotating magnetic field are Measurements and experiments investigated experimentally and theoretically. The All the materials-may be metals, semiconductors or rotational motion of the drop is most easily studied insulators-have size dependent physical-chemical experimentally for the non-axis symmetric shape. This properties below a certain critical size. However, for most effect may contribute to the difference in the experimental of the materials this critical size is below ~100 nm. At and theoretical results for the rotation frequency of the such a small size even the shape of the material and elongated drop (Lebedev et al., 2003). The equilibrium interactions between nano materials decide the magnetization of concentrated ferro fluids described by a properties of the material. This opens up a huge system of polydisperse dipolar hard spheres is calculated possibility of tailor-making the materials, which have as a function of the internal magnetic field using the Born- different properties just due to their size, shape and/or Mayer or cluster expansion technique (Huke & Lu¨cke, assembly. Measurements on single nano particles, rods, 2003). The characterization has been much useful for tubes etc. would inherently be difficult, though not applications of ferro fluid. impossible. However measurements on nano crystalline Preparation of ferro fluid solids, thin films etc. are possible using some There are several methods of synthesis of magnetite conventional methods. nano particles. After some initial trials, ferrofluid is Results of X – ray diffraction (XRD) prepared using two methods: The first method uses The nano particles are separated out from the flammable substances and generates heat and toxic as a precipitate by using a centrifuge approximately at fumes. The ingredients are: ammonia - Oleic acid, ferric 2000 to 3000 rpm. Precipitate is washed with , Photograph 1. Ferro fluid with and without magnet. Graph 1. XRD plot

Research article “Smart fluid” S.B.Purohit et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol.

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Indian Journal of Science and Technology Vol. 4 No. 11 (Nov 2011) ISSN: 0974- 6846 ethanol, to remove unreacted chemicals or by products. Damping coefficient of ferro fluid compared with other Precipitates are then dried to get sample in the form o standard fluid powder. The filtered particles from the ferro fluid prepared Photograph 2. Vibration Fundamental Training System (VFT) chemically, are taken to XRD machine –Brukar D8 discover. As per the Graph 1 obtained from XRD, the diffraction peaks in nano crystalline particles are broadened compared to polycrystalline solid. The broadening is caused by the nano particle size. For extremely small particle size <2 nm, the broadening of diffraction peaks becomes very large. The average particle size is 12 nm. Results from scanning electron microscope (SEM) In SEM the electron beam can be focused to a very small spot size using electrostatic lenses. The fine beam is scanned on the sample surface using a scan generator The damping behavior of ferro fluid is observed on and back scattered electrons are collected by an Vibration Fundamental Training System (VFT). A appropriate detector. The SEM result of fine filtered container is filled with the ferro fluid and a flat disc floats particles shows the maximum particle size to be 32 nm. on the fluid. The disc from the upper side is attached to a Turbidity measurement spring and together the system constitutes a spring and a The experimental set up for turbidity measurement is dash pot system. The system is made to vibrate as per focused on first putting the prepared ferro fluid in the the input data (Photograph 2). centrifuge at 2000 rpm and rotating for different periods to The in house prepared ferro fluid has kerosene as the maximum value of five minutes. Assuming that the field carrier fluid, and therefore the kerosene is taken as the conditions will not be worst than this for simple reference fluid for comparison with the ferro fluid. Shock applications like in a shock absorber. The liquid is taken absorber suspension oil is taken as other fluid for out from centrifuge and the turbidity is measured in the EI comparison with the ferro fluid. digital turbidity meter. The colloidal suspension of the [5.a] Kerosene as a damping fluid differential heavier particles of magnetite, Fe₃O₄ in the (Graph no.3 ) carrier fluid result into momentary separation for few Graph 3. Damping characteristics of kerosene seconds after 2000 Graph 2. Turbidity v/s time rpm. The Graph 1 shows the variations in turbidity with time at 2000 rpm. For different rpm values the results are not repetitive. After some The natural frequency of the system with kerosene is time, slowly the turbidity returns to its initial value and the effect of rpm detected as, f = 5.88659 Hz, The circular frequency , ωn vanishes. The particles do not settle at the bottom and = 36.9865 rad/s ,The logarithmic decrement ,δ = 0.395,The damping ratio ,ζ = 0.0627, The damping the liquid remains in the colloidal form in general. The frequency , ω = 36.8391 rad/s, c = 3.69865,The initial filtered particles were repeatedly filtered to finally d c damping coefficient, c = ζ c = 0.23190 Ns/m arrive at the turbidity meter value wherein the separation c [5.b] Front shock absorber oil as a damping fluid of the fine particles does not occur. Measurement of density (Graph no.4) There is a variation in the density for different Graph. 4. Damping characteristics of shock absorber oil quantities of ferro fluid due to the reason that the samples are taken from different lot of preparations and the variation in the particle sizes. For the same lot and with different sample sizes the variation is not considerable. To get the consistency in the results the ferro particles were filtered repeatedly and added with the carrier fluid till the repeat results were obtained. The density of ferrofluid= 1.1423 gms/ml.

Research article “Smart fluid” S.B.Purohit et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol.

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Indian Journal of Science and Technology Vol. 4 No. 11 (Nov 2011) ISSN: 0974- 6846

The natural frequency of the system with Shock is difficult to measure in magnetic field. Modification is absorber oil is detected as, f = 5.88268 Hz, The circular done on a redwood viscometer and setting is done frequency , ωn = 36.9608 rad/s, The logarithmic comparing with the earlier readings taken on conventional decrement ,δ = 0.348, The damping ratio ,ζ = 0.0553, The redwood viscometer (Photograph 3); damping frequency , ωd = 36.8462rad /s, cc = 3.6846 Photograph 3. A conventional redwood viscometer Ns/m. The damping coefficient, c = 0.2037 Ns/m. [5.c ] ‘In house made Ferro fluid’ as a damping fluid (Graph no.5) Graph 5. Damping characteristics of ferro fluid

Viscosity of Shock absorber oil (a standard for comparison) using conventional redwood viscometer The natural frequency of the system with Ferro fluid is presented in Table 1. Viscosity measurement on detected as, f = 5.88192 Hz, The circular frequency , ω = n magnetised redwood viscometer presented in Table 2. 36.9571rad/s, The logarithmic decrement ,δ = 0.413,The Photographs of the components taken of the modified damping ratio ,ζ = 0.06559, The damping frequency , ω d viscometer prepared in house (Photograph.4; Graph 7; = 36.877 rad/s, c = 3.6957 Ns/m, The damping c Fig.1). coefficient, c = 0.2418 Ns/m [5.d ] ‘Ferro fluid in magnetic field ‘as a damping fluid Table 1. Redwood viscometer O O (Graph no.6) Water T ( C) Oil T ( C) Time in sec. for flow of 50ml of oil Graph 6. Damping characteristics of ferro fluid 20 20 94 in magnetic field 29 29 65 47 47 45 Table 2. Modified viscometer Name of fluid/ position of Time to flow 50 ml fluid (in sec) tip X=8 mm X=10 X=12 mm mm Ferrow fluid (with magnet) 43.32 46.49 1045.07 Ferrow fluid (without 42.47 43.57 63.83 magnet) The natural frequency of the system with ferro fluid in Kerosene 39 41.09 54.66 magnetic fieldis detected as, f = 5.90569 Hz, The Shock up oil 176.87 174.09 175.88 circular frequency , ωn = 37.1065 rad/s, The logarithmic Water 39.73 39.51 47.66 decrement ,δ = 0.225, The damping ratio ,ζ = Photograph 4.Various modified components 0.03578,The damping frequency , ωd = 37.0827 rad /s, cc = 3.7106,The damping coefficient, c = 0. 8348 Ns/m. The damping coefficient of ferro fluid is compared to the standards selected. As the ferrofluid is subjected to the magnetic field, the damping coefficient value changes considerably. Viscosity measurement Fluid can be measured in several ways with different viscometers. Liquid viscosities are sometimes determined by measuring the time required for a given quantity of liquid to flow by through a precision opening. A liquid of high mass density flows through the viscometer more quickly than does a less dense liquid of same absolute viscosity. In the magnetic field ferrofluid changes its viscosity and therefore it’s apparent viscosity

Research article “Smart fluid” S.B.Purohit et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol.

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Indian Journal of Science and Technology Vol. 4 No. 11 (Nov 2011) ISSN: 0974- 6846 Graph 7. Viscosity measurements for different settings of Fig.1. Modified Redwood viscometer viscometer.

Conclusion Some of the mechanical properties have been observed using different experimental techniques which will enable further use of the ferro fluid to various applications. With the method of preparation of ferro fluid, the mechanical properties like: density, particle size, turbidity, viscosity with and without magnetic field are measured. The ferro fluid prepared in house contains nano particles. The nano particles range up to 32 nm. 2. Alexander V Lebedev, Andreas Engel, Konstantin I The average particle size is 12 nm. At this value the Morozov and Heiko Bauke (2003) Ferrofluid drops in density variation and the turbidity settlement stabilizes. rotating magnetic fields. New J. Phys. 5, 57.1–57.20. From SEM photograph it appears that the nm particles doi:10.1088/1367-2630/5/1/357. are mostly spheres. The effect of external magnetic field 3. Brousseau D (2008) Wave front correction with a ferro on the property of ferro fluid, like viscosity cannot be fluid deformable mirror, experimental results and measured by the conventional method and therefore recent developments. Ph.D. Thesis, Universite’ Lavel. modification is done on the conventional redwood 4. Hrovat D (1998) Survey of advanced suspension viscometer. The modified viscometer is calibrated with developments and related optimal control applications. conventional viscometer with standard fluid and then the Automatica. 33(10), 1781-1817. viscosity is compared for the ferro fluid. One can get the 5. Huke B and Lu¨cke M (2003) Magnetization of desired viscosity of the ferro fluid after the setting the concentrated polydisperse ferrofluids: Cluster magnetic field. When the ferrofluid is subjected to the expansion. Physical Rev. E 67, 051403. magnetic field then the damping coefficient value 6. Ravaud R and Lemarquand G (2009) Mechanical changes considerably. For a shock absorber where semi properties of a ferro fluid seal. Three dimensional active suspension is desirable, there the use of the ferro analytical approach based on the Columbian model. fluid with coupling (c = 0.8348 N –sec/m) and Prog. in Electromagnetics Res. 13, 385–407. decoupling(c = 0. 2418 N –sec/m) with the magnetic field 7. Tomasz Strek (2005) Finite element simulation of Heat for the instant change in damping coefficient is transfer in ferro fluid. Intl. J. Appl. Mechanics & Engg. recommended. It is thus possible to get the instant 10, 103-105. change in the viscosity and therefore the instant change 8. Upadhyay Shail (2006) Simple technique to measure in the damping characteristics of the viscous fluid. volume of solid body using ferro fluid. Physics Edu. References April- June . pp:21-26. 1. Afkhami S, Renardy Y, Renardy M, Riffle JS and St. Pierre TG (2008) Numerical modeling of ferrofluid th droplets in magneti fields. 15 Intl. Congress on Rheol. The Soc. Rheol. 80th Annual Meeting.pp:521- 526.

Research article “Smart fluid” S.B.Purohit et al. Indian Society for Education and Environment (iSee) http://www.indjst.org Indian J.Sci.Technol.